The rapid development of laser technology has made portable laser systems with high power and energy available. The lasers are widely used for many applications and have greatly advanced scientific research. As they are used everywhere, the odds of a laser beam accidentally hitting a person are increasing. Even low-power lasers can damage human eyes or photosensors. As such, studies of optical power limiting and design of devices are receiving lot of interest. Several optical techniques with various materials including inorganic, organic and biological molecules have been used for such applications. Nonlinear absorption effects such as reverse saturable absorption including excited state absorption and multi-photon absorption have been widely studied with high power pulsed lasers for limiting power. Light scattering is also used to limit the optical power when a strong beam is incident on some materials and it can enhance the nonlinear absorption. Another important nonlinear optical effect used for limiting power is beam diffusing, which originates from the change of spatial distribution of the refractive index and manifests as self-defocusing, beam fanning (diffusive photovoltaic thermal effects), and the Kerr effect. The filtering features associated with the holographic technique and photonic bandgap materials are also useful for power-limiting applications.
Recently, polarization rotation in resonant Faraday media sandwiched between crossed polarizers and bacteriorhodopsin materials placed between a pair of parallel polarizers has been studied theoretically and experimentally and can be used for optical limiting applications. These polarization rotation techniques may offer many advantages such as, for example, low-fluence threshold, high-intensity range, and ease of improvement with new materials for practical applications, particularly for protecting human eyes and sensitive optical sensors that can be damaged by even low-power laser beams. However, all these systems have been only demonstrated in the laboratory with high power laser systems and are far from practical in different applications. There remains a need for systems and methods to limit the power in optical systems.